tbh, I feel like promoting KH to a Disney fan feels like scam with how shafted Disney stuff are and with how Disney world plot are more often rehash o the movie, only pixar worlds have tweaks bc pixar is rebel like that. I want to be honest that KH is those kind of crackpot plot kind of fiction, not "lying" it's "just" crossover.
Considering Disney, as a corporation, had done series like House of Mouse, Once Upon a Time, and in more recent years had Phineas and Ferb crossover specials with both Marvel and
Star Wars, it’s more surprising that they didn’t make a series already.
And in fairness to at least the first KH game, the worlds weren’t complete movie rehashes, Olympus had its story take place after the movie much like the Pixar worlds, Wonderland ended on a cliffhanger regarding Alice until a later world revealed her fate, and Aladdin found out about the existence of other worlds and entrusted Sora with finding Jasmine with Genie’s help.
That said, I can agree that the crossover angle wouldn’t be enough. To really sell a KH show, there’d need to be more of a focus on th original stuff first before getting into the inevitable crossover aspect. Maybe a 3-episode pilot in the vein of Netflix Voltron could work: setup the characters, the world and then set the story going from there.